use strict;
my $str = '{89695C16_C0FF_4E7C_9BB2_8B50FAC9D371}';
my $regex = qr/{\K([A-Z0-9]{8})_([A-Z0-9]{4})_([A-Z0-9]{4})_([A-Z0-9]{4})_([A-Z0-9]{12})(?=})/mp;
my $subst = '$1-$2-$3-$4-$5';
my $result = $str =~ s/$regex/$subst/rg;
print "The result of the substitution is' $result\n";
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html