diff --git a/day13/sol.tcl b/day13/sol.tcl
index 315dcc8..5bff207 100755
--- a/day13/sol.tcl
+++ b/day13/sol.tcl
@@ -2,7 +2,7 @@
 source ../prelude.tcl
 
 set input stdin
-set patterns [split [string map {"\n\n" "|"} [string trim [read $input]]] "|"]
+set patterns [splitstr [trim [read $input]] "\n\n"]
 set patterns [lmap p $patterns {split $p "\n"}]
 puts "$patterns"
 
@@ -10,9 +10,9 @@ proc reflect pattern {
     set total 0
     foreach pat [list $pattern [transpose $pattern]] factor {100 1} {
         #puts "reflect $pat"
-        for {set i 1} {$i < [llength $pat]} {incr i} {
+        for {set i 1} {$i < [llen $pat]} {incr i} {
             set ok 1
-            for {set j 0} {$i + $j < [llength $pat] && $i-$j-1 >= 0} {incr j} {
+            for {set j 0} {$i + $j < [llen $pat] && $i-$j-1 >= 0} {incr j} {
                 if {[lindex $pat $i+$j] ne [lindex $pat [expr {$i-$j-1}]]} {
                     set ok 0
                     break
@@ -32,9 +32,9 @@ proc fix pattern {
     foreach pat [list $pattern [transpose $pattern]] factor {100 1} {
         #puts "reflect $pat"
         array unset smudges
-        for {set i 1} {$i < [llength $pat]} {incr i} {
+        for {set i 1} {$i < [llen $pat]} {incr i} {
             set diff 0
-            for {set j 0} {$i + $j < [llength $pat] && $i-$j-1 >= 0} {incr j} {
+            for {set j 0} {$i + $j < [llen $pat] && $i-$j-1 >= 0} {incr j} {
                 incr diff [distance [lindex $pat $i+$j] [lindex $pat [expr {$i-$j-1}]]]
                 if {$diff > 1} break
             }
@@ -64,7 +64,7 @@ proc column {lst i} {
 }
 
 proc transpose pat {
-    set C [string length [lindex $pat 0]]
+    set C [slen [lindex $pat 0]]
     set out {}
     for {set i 0} {$i < $C} {incr i} {
         lappend out [column $pat $i]
diff --git a/prelude.tcl b/prelude.tcl
index ddd3b06..2650a04 100644
--- a/prelude.tcl
+++ b/prelude.tcl
@@ -4,6 +4,11 @@ namespace import tcl::mathfunc::max
 
 proc {#} args {}
 
+proc llen {lst} { return [llength $lst] }
+proc slen {str} { return [string length $str] }
+proc trim args { return [uplevel [concat string trim $args]] }
+proc replace {str a b} { return [string map [list $a $b] $str] }
+
 proc ladd {list} {
     set t 0
     foreach x $list { incr t $x }
@@ -16,6 +21,12 @@ proc lmul {list} {
     return $p
 }
 
+# split s on a substring
+proc splitstr {s sep} {
+    # replace $sep with ascii char 30, aka "record separator"
+    return [split [replace $s $sep "\x1E"] "\x1E"]
+}
+
 proc must_regexp args {
     if {! [uplevel [concat regexp $args]]} {
         error "regexp failed"