<b_jonas> perl -e for $e ("i","u"){ $f="bin/date$e"; open my$i,"<",$f or die "error open $f r"; local$/; $s=<$i> or die; $s=~s/"\\+%Y/\\${d:+-d "\\$d"} $&/ or die; open $o,">",$f or die "error open $f w: $!"; print $o $s or die; close $o or die; print "OK $f\\n" }

'Collatz problem calculator
'Programmed by Jannis Harder (jix), 2005
1[1?,1~10:2,0>-1,2=*0,2>-2,0+*2,0+*1,0-48]1
2[0#,5=10,5$,0~1:0,1=*0,1|1,1<-1:3,0>1]2
3[1=*0,0+*1,0+*1,0+1]2