c:\@Work\Perl\monks>perl -wMstrict -le
"my $curdir   = 'Y:\Music\Schubert\Lieder\Terfel';
 my $startdir = 'Y:\mUsIc';
 ;;
 my $plsname = $curdir;
 $plsname =~ s{ \A (?i) \Q$startdir\E \\ (.+) \z }
              { (my $r = $1) =~ tr{\\}{_};  $r . '.pls'; }xmse;
 print qq{'$plsname'};
"
'Schubert_Lieder_Terfel.pls'