c:\@Work\Perl\monks>perl -wMstrict -le
"my $curdir   = 'Y:\Music\Schubert\Lieder\Terfel';
 my $startdir = 'Y:\mUsIc';
 ;;
 my $plsname =
   $curdir =~ s{ \A (?i) \Q$startdir\E \\? }{}xmsr =~ tr{\\}{_}r . '.pls';
 print qq{'$plsname'};
"
'Schubert_Lieder_Terfel.pls'