use Regexp::Common qw[ delimited ];

my $P1 = '../matrix-ops/matopmul.mk';
my $P2 = 'C:\matrix-ops\matopmul.mk';

print "P1 has path\n" if ($P1 =~ /$RE{delimited}{-delim => '\/'}/ );
print "P2 has path\n" if ($P2 =~ /$RE{delimited}{-delim => '\/'}/ );