Determine if a string starts with an upper-case character in Perl

Question

I need to make a subroutine in Perl which determines if a string starts with an upper-case character. What I have so far is the following:

sub checkCase {
    if ($_[0] =~ /^[A-Z]/) {
        return 1;
    }
    else {
        return 0;
    }
}

$result1 = $checkCase("Hello");
$result2 = $checkCase("world");

Answer 1

Your code is fine as long as you remove the $ from the front of your subroutine call. A dollar sign indicates a scalar value, and the calls should look like

$result1 = checkCase("Hello");
$result2 = checkCase("world");

Your subroutine is also unnec essarily long. The regex match returns a true/false value, and you are using that value to return different true/false values 1 or 0. Much better to return the result of the regex match directly.

Finally, if you are working outside ASCII characters then you may want to use the Uppercase Letter Unicode category, which is encoded using \p{Lu}.

I hope this variation on your code is useful. I have changed the name of the subroutine slightly because it is standard practice to use just lower case letters and underscores for variable and subroutine identifiers. Upper case letters are reserved for globals like package names.

sub check_case {
  $_[0] =~ /^\p{Lu}/
}

print check_case('Hello') ? 'YES' : 'NO', "\n";
print check_case('world') ? 'YES' : 'NO', "\n";

Answer 2

That's almost correct. But [A-Z] might not match uppercase accented characters depending on your locale. Better to use /^[[:upper:]]/.

Also your subroutine invocations shouldn't have the $ character in front of them. I.e. they should be:

$result1 = checkCase("Hello");
$result2 = checkCase("world");