Re: transliteration d flag not working as expected

[LanX]

you can achieve the desired result by combining two tr

  DB<112> $_="alter"
 => "alter"

  DB<113> tr/this//cd                 # delete anything except t,h,i,s
 => 4

  DB<114> $_
 => "t"

  DB<115> tr/this/flip/                # translate
 => 1

  DB<116> $_
 => "f"

[AnomalousMonk]

You could also do it with a single  s/// substitution, although it is messier and almost certainly slower than a double-tr/// approach:

>perl -wMstrict -le
"my %xlate = qw(t f  h l  i i  s p);
 ;;
 my $s = 'alters';
 $s =~ s{ . }{ $xlate{${^MATCH}} // '' }xmsgpe;
 print qq{'$s'};
"
'fp'

[LanX]

Not sure if it's slower, 'tr///' doesn't allow variable interpolation.

Using it twice in a DRY way means putting the pattern into a variable which leads to eval :(

        Because the transliteration table is built at compile time, ne
+ither
           the SEARCHLIST nor the REPLACEMENTLIST are subjected to dou
+ble
           quote interpolation.  That means that if you want to use va
+riables,
           you must use an eval():

[AnomalousMonk]

What I had in mind was that  s/// would be messier/slower if interpolation was unnecessary, as the OPed problem statement seemed to indicate. I agree that if interpolation becomes necessary,  s/// is almost certainly preferable to an eval approach.