$ perl -wE 'my $re = qr{A}g' Unknown regexp modifier "/g" at -e line 1, near "= " Execution of -e aborted due to compilation errors. #### $ perl -wE 'use re "/g"' Unknown regular expression flag "g" at -e line 1. #### $ perl -wE 'my ($p, $f) = (A => "x"); my $re = qr{(?$f: $p )}; say $re' (?^u:(?x: A )) #### $ perl -wE 'qr{(?g:)}' Useless (?g) - use /g modifier in regex; marked by <-- HERE in m/(?g <-- HERE :)/ at -e line 1.