...
my $text;
my $match = 0;
my $regex = qr/$ARGV[1]/;

{
    local $/;                       # enable "slurp" mode
    $text = <$fh>;                  # read whole file
}

while ($text =~ /$regex/gms)
{
    print "Match found\n";
    $match = 1;
}

print "No matches found\n" unless $match;