use strict;
my $str = '{"id":1145585,"label":"1145585: Project Z"}
{"id":1150322,"label":"1150322: Project Waka 1"}|{"id":1150365,"label":"1150365: Project Waka 2"}
{"id":1149240,"label":"1149240: Analysis of Technical Options"}|{"id":1149258,"label":"1149258: Check and Report"}
{"id":1148925,"label":"1148925: Change Management Review"}|{"id":1148920,"label":"1148920: Follow-Up Meetings"}|{"id":1148923,"label":"1148923: Launch Date Definition"}';
my $regex = qr/\{"id":([0-9]*),[^}]*\}\|?/p;
my $subst = '\\1;';
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