Perl sample that illustrate the usage of (duplicated) named subpatterns

rx_name.pl

use v5.10.01;
use strict;
use warnings;

my $rx = 
qr{
  # match contain groups 'file' + 'line'
	\bfile:? (?<file>.+) \s at \s line \s (?<line>\d+)
	# match contain only 'line'
	| \s at \s line \s (?<line>\d+) 
	# match contain only 'file'
	| \bfile:? (?<file>.+)
}x;

my @test_data = ( 
	# file + line
	'importing file: c:/titi/toto/tutu.tata at line 42 : unknown error!',
	# file only
	'importing file: c:/titi/toto/tutu.tata.',
	# line only
	'error at line 101 : missing EOL!',
);

foreach my $data ( @test_data ){
	say "data: ", $data;
	if($data =~ /$rx/){ 
	   # the hash %+ contain named groups of the last regex match.
	   say "\tfile: ", $+{file} if $+{file};
	   say "\tline: ", $+{line} if $+{line};
	}
	else{
		say "\tno match!";
	}
}

__END__