diff --git a/test/cases/dsl-unformat/0001/cmd b/test/cases/dsl-unformat/0001/cmd
new file mode 100644
index 000000000..6add080d4
--- /dev/null
+++ b/test/cases/dsl-unformat/0001/cmd
@@ -0,0 +1 @@
+mlr -n put -f ${CASEDIR}/mlr
diff --git a/test/cases/dsl-unformat/0001/experr b/test/cases/dsl-unformat/0001/experr
new file mode 100644
index 000000000..d8ae67054
--- /dev/null
+++ b/test/cases/dsl-unformat/0001/experr
@@ -0,0 +1 @@
+mlr: function unformat invoked with 0 arguments; expected 2
diff --git a/test/cases/dsl-unformat/0001/expout b/test/cases/dsl-unformat/0001/expout
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/cases/dsl-unformat/0001/mlr b/test/cases/dsl-unformat/0001/mlr
new file mode 100644
index 000000000..23c208045
--- /dev/null
+++ b/test/cases/dsl-unformat/0001/mlr
@@ -0,0 +1,3 @@
+end {
+  print unformat()
+}
diff --git a/test/cases/dsl-unformat/0001/should-fail b/test/cases/dsl-unformat/0001/should-fail
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/cases/dsl-unformat/0002/cmd b/test/cases/dsl-unformat/0002/cmd
new file mode 100644
index 000000000..6add080d4
--- /dev/null
+++ b/test/cases/dsl-unformat/0002/cmd
@@ -0,0 +1 @@
+mlr -n put -f ${CASEDIR}/mlr
diff --git a/test/cases/dsl-unformat/0002/experr b/test/cases/dsl-unformat/0002/experr
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/cases/dsl-unformat/0002/expout b/test/cases/dsl-unformat/0002/expout
new file mode 100644
index 000000000..ffba14cee
--- /dev/null
+++ b/test/cases/dsl-unformat/0002/expout
@@ -0,0 +1 @@
+(error)
diff --git a/test/cases/dsl-unformat/0002/mlr b/test/cases/dsl-unformat/0002/mlr
new file mode 100644
index 000000000..35cf7e6a6
--- /dev/null
+++ b/test/cases/dsl-unformat/0002/mlr
@@ -0,0 +1,3 @@
+end {
+  print unformat(1, 2)
+}
diff --git a/test/cases/dsl-unformat/0003/cmd b/test/cases/dsl-unformat/0003/cmd
new file mode 100644
index 000000000..6add080d4
--- /dev/null
+++ b/test/cases/dsl-unformat/0003/cmd
@@ -0,0 +1 @@
+mlr -n put -f ${CASEDIR}/mlr
diff --git a/test/cases/dsl-unformat/0003/experr b/test/cases/dsl-unformat/0003/experr
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/cases/dsl-unformat/0003/expout b/test/cases/dsl-unformat/0003/expout
new file mode 100644
index 000000000..ffba14cee
--- /dev/null
+++ b/test/cases/dsl-unformat/0003/expout
@@ -0,0 +1 @@
+(error)
diff --git a/test/cases/dsl-unformat/0003/mlr b/test/cases/dsl-unformat/0003/mlr
new file mode 100644
index 000000000..ce157db14
--- /dev/null
+++ b/test/cases/dsl-unformat/0003/mlr
@@ -0,0 +1,3 @@
+end {
+  print unformat("12m34s", "{}:{}")
+}
diff --git a/test/cases/dsl-unformat/0004/cmd b/test/cases/dsl-unformat/0004/cmd
new file mode 100644
index 000000000..6add080d4
--- /dev/null
+++ b/test/cases/dsl-unformat/0004/cmd
@@ -0,0 +1 @@
+mlr -n put -f ${CASEDIR}/mlr
diff --git a/test/cases/dsl-unformat/0004/experr b/test/cases/dsl-unformat/0004/experr
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/cases/dsl-unformat/0004/expout b/test/cases/dsl-unformat/0004/expout
new file mode 100644
index 000000000..44e2ace7e
--- /dev/null
+++ b/test/cases/dsl-unformat/0004/expout
@@ -0,0 +1 @@
+[1, 2]
diff --git a/test/cases/dsl-unformat/0004/mlr b/test/cases/dsl-unformat/0004/mlr
new file mode 100644
index 000000000..25fc3fded
--- /dev/null
+++ b/test/cases/dsl-unformat/0004/mlr
@@ -0,0 +1,3 @@
+end {
+  print unformat("{}:{}", "1:2")
+}
diff --git a/test/cases/dsl-unformat/0005/cmd b/test/cases/dsl-unformat/0005/cmd
new file mode 100644
index 000000000..6add080d4
--- /dev/null
+++ b/test/cases/dsl-unformat/0005/cmd
@@ -0,0 +1 @@
+mlr -n put -f ${CASEDIR}/mlr
diff --git a/test/cases/dsl-unformat/0005/experr b/test/cases/dsl-unformat/0005/experr
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/cases/dsl-unformat/0005/expout b/test/cases/dsl-unformat/0005/expout
new file mode 100644
index 000000000..ffba14cee
--- /dev/null
+++ b/test/cases/dsl-unformat/0005/expout
@@ -0,0 +1 @@
+(error)
diff --git a/test/cases/dsl-unformat/0005/mlr b/test/cases/dsl-unformat/0005/mlr
new file mode 100644
index 000000000..3f0e125e0
--- /dev/null
+++ b/test/cases/dsl-unformat/0005/mlr
@@ -0,0 +1,3 @@
+end {
+  print unformat("{}:{}", "1")
+}
diff --git a/test/cases/dsl-unformat/0006/cmd b/test/cases/dsl-unformat/0006/cmd
new file mode 100644
index 000000000..6add080d4
--- /dev/null
+++ b/test/cases/dsl-unformat/0006/cmd
@@ -0,0 +1 @@
+mlr -n put -f ${CASEDIR}/mlr
diff --git a/test/cases/dsl-unformat/0006/experr b/test/cases/dsl-unformat/0006/experr
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/cases/dsl-unformat/0006/expout b/test/cases/dsl-unformat/0006/expout
new file mode 100644
index 000000000..4b0e5443d
--- /dev/null
+++ b/test/cases/dsl-unformat/0006/expout
@@ -0,0 +1 @@
+[1, ""]
diff --git a/test/cases/dsl-unformat/0006/mlr b/test/cases/dsl-unformat/0006/mlr
new file mode 100644
index 000000000..07b34bdf5
--- /dev/null
+++ b/test/cases/dsl-unformat/0006/mlr
@@ -0,0 +1,3 @@
+end {
+  print unformat("{}:{}", "1:")
+}
diff --git a/test/cases/dsl-unformat/0007/cmd b/test/cases/dsl-unformat/0007/cmd
new file mode 100644
index 000000000..6add080d4
--- /dev/null
+++ b/test/cases/dsl-unformat/0007/cmd
@@ -0,0 +1 @@
+mlr -n put -f ${CASEDIR}/mlr
diff --git a/test/cases/dsl-unformat/0007/experr b/test/cases/dsl-unformat/0007/experr
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/cases/dsl-unformat/0007/expout b/test/cases/dsl-unformat/0007/expout
new file mode 100644
index 000000000..44e2ace7e
--- /dev/null
+++ b/test/cases/dsl-unformat/0007/expout
@@ -0,0 +1 @@
+[1, 2]
diff --git a/test/cases/dsl-unformat/0007/mlr b/test/cases/dsl-unformat/0007/mlr
new file mode 100644
index 000000000..25fc3fded
--- /dev/null
+++ b/test/cases/dsl-unformat/0007/mlr
@@ -0,0 +1,3 @@
+end {
+  print unformat("{}:{}", "1:2")
+}
diff --git a/test/cases/dsl-unformat/0008/cmd b/test/cases/dsl-unformat/0008/cmd
new file mode 100644
index 000000000..6add080d4
--- /dev/null
+++ b/test/cases/dsl-unformat/0008/cmd
@@ -0,0 +1 @@
+mlr -n put -f ${CASEDIR}/mlr
diff --git a/test/cases/dsl-unformat/0008/experr b/test/cases/dsl-unformat/0008/experr
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/cases/dsl-unformat/0008/expout b/test/cases/dsl-unformat/0008/expout
new file mode 100644
index 000000000..84d44b3d8
--- /dev/null
+++ b/test/cases/dsl-unformat/0008/expout
@@ -0,0 +1 @@
+[1, "2:3"]
diff --git a/test/cases/dsl-unformat/0008/mlr b/test/cases/dsl-unformat/0008/mlr
new file mode 100644
index 000000000..391ba6b80
--- /dev/null
+++ b/test/cases/dsl-unformat/0008/mlr
@@ -0,0 +1,3 @@
+end {
+  print unformat("{}:{}", "1:2:3")
+}
diff --git a/test/cases/dsl-unformat/0009/cmd b/test/cases/dsl-unformat/0009/cmd
new file mode 100644
index 000000000..6add080d4
--- /dev/null
+++ b/test/cases/dsl-unformat/0009/cmd
@@ -0,0 +1 @@
+mlr -n put -f ${CASEDIR}/mlr
diff --git a/test/cases/dsl-unformat/0009/experr b/test/cases/dsl-unformat/0009/experr
new file mode 100644
index 000000000..7649c9f5e
--- /dev/null
+++ b/test/cases/dsl-unformat/0009/experr
@@ -0,0 +1,11 @@
+mlr: cannot parse DSL expression.
+Parse error on token ""<abc:defi)
+" at line 2 column 29.
+Expected one of:
+  { ( ) field_name $[ braced_field_name $[[ $[[[ full_srec oosvar_name @[
+  braced_oosvar_name full_oosvar all non_sigil_name float int + - .+ .- !
+  ~ string_literal regex_case_insensitive int_literal float_literal boolean_literal
+  null_literal const_M_PI const_M_E panic [ ctx_IPS ctx_IFS ctx_IRS ctx_OPS
+  ctx_OFS ctx_ORS ctx_FLATSEP ctx_NF ctx_NR ctx_FNR ctx_FILENAME ctx_FILENUM
+  env func
+
diff --git a/test/cases/dsl-unformat/0009/expout b/test/cases/dsl-unformat/0009/expout
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/cases/dsl-unformat/0009/mlr b/test/cases/dsl-unformat/0009/mlr
new file mode 100644
index 000000000..1e9c3316f
--- /dev/null
+++ b/test/cases/dsl-unformat/0009/mlr
@@ -0,0 +1,3 @@
+end {
+  print unformat("<{}:{}>", "<abc:defi)
+}
diff --git a/test/cases/dsl-unformat/0009/should-fail b/test/cases/dsl-unformat/0009/should-fail
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/cases/dsl-unformat/0010/cmd b/test/cases/dsl-unformat/0010/cmd
new file mode 100644
index 000000000..6add080d4
--- /dev/null
+++ b/test/cases/dsl-unformat/0010/cmd
@@ -0,0 +1 @@
+mlr -n put -f ${CASEDIR}/mlr
diff --git a/test/cases/dsl-unformat/0010/experr b/test/cases/dsl-unformat/0010/experr
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/cases/dsl-unformat/0010/expout b/test/cases/dsl-unformat/0010/expout
new file mode 100644
index 000000000..8b827807c
--- /dev/null
+++ b/test/cases/dsl-unformat/0010/expout
@@ -0,0 +1 @@
+[5, 18, 47, 22]
diff --git a/test/cases/dsl-unformat/0010/mlr b/test/cases/dsl-unformat/0010/mlr
new file mode 100644
index 000000000..9e23e9d06
--- /dev/null
+++ b/test/cases/dsl-unformat/0010/mlr
@@ -0,0 +1,3 @@
+end {
+  print unformat("{}-{}:{}:{}", "5-18:47:22")
+}
diff --git a/test/cases/dsl-unformat/0011/cmd b/test/cases/dsl-unformat/0011/cmd
new file mode 100644
index 000000000..6add080d4
--- /dev/null
+++ b/test/cases/dsl-unformat/0011/cmd
@@ -0,0 +1 @@
+mlr -n put -f ${CASEDIR}/mlr
diff --git a/test/cases/dsl-unformat/0011/experr b/test/cases/dsl-unformat/0011/experr
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/cases/dsl-unformat/0011/expout b/test/cases/dsl-unformat/0011/expout
new file mode 100644
index 000000000..8a1a13ff7
--- /dev/null
+++ b/test/cases/dsl-unformat/0011/expout
@@ -0,0 +1 @@
+["5", "18", "47", "22"]
diff --git a/test/cases/dsl-unformat/0011/mlr b/test/cases/dsl-unformat/0011/mlr
new file mode 100644
index 000000000..efe56dc1b
--- /dev/null
+++ b/test/cases/dsl-unformat/0011/mlr
@@ -0,0 +1,3 @@
+end {
+  print unformatx("{}-{}:{}:{}", "5-18:47:22")
+}
diff --git a/test/cases/dsl-unformat/x b/test/cases/dsl-unformat/x
new file mode 100644
index 000000000..36c250aab
--- /dev/null
+++ b/test/cases/dsl-unformat/x
@@ -0,0 +1 @@
+  print unformat("{}:{}", "1")
diff --git a/todo.txt b/todo.txt
index 4709a00b8..491137cf0 100644
--- a/todo.txt
+++ b/todo.txt
@@ -6,12 +6,15 @@ RELEASES
 ================================================================
 FEATURES
 
-k better print-interpolate with {} etc
 ! Better functions for values manipulation, e.g. easier conversion of strings like "$1,234.56" into numeric values
+  o note on is_error(x) (or string(x) == "(error)")
+  ?  dhms w/ optional separgs -- ? what about fenceposting? ["d","h","m","s"] vs ["-",":",":",""] -- ?
   o 'Ability to specify some formats that are fixed. Like we can process
     "5d18h53m20s" format in *dhms* commands, but what about "5-18:53:20"? This is
     a common format used by the SLURM resource manager.'
-  o generalize dhms w/ sscanf-style something -- ?
+  o linked-to faqent w/ -f -s etc ...
+  o ... AND, if it's frequent then submit a feature request b/c other people probably also would like it! :)
+k better print-interpolate with {} etc
 ! sysdate, sysdate_local; datediff ...
 ! strmatch https://github.com/johnkerl/miller/issues/77#issuecomment-538790927
 ! sliding window / moving average