in reply to check if its a number

I was going to post something else, but in the process I tried this: 
my $foo = 'name';
print $foo + 1;

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Perl warns me "Argument "name" isn't numeric in addition (+)" How does Perl know it isn't a number? Is the method available through a function?

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Re^2: check if its a number
by nobull (Friar) on Apr 12, 2008 at 14:23 UTC
    Yes you can write a function that tells you if a given string triggers the warning. 

    
sub perl_thinks_it_is_number {
    eval { 
        use warnings FATAL => 'numeric';
        no warnings 'void';
        0+shift;
        1;
    }
}

print "'foo' isn't a number\n" 
    unless perl_thinks_it_is_number 'foo';

print "'17' is a number\n"
    if perl_thinks_it_is_number '17';

    [download]
    Note that this will consider '00' and some other oddities to be a number. You are probably better sticking with other answers elsewhere in this thread.
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Re^2: check if its a number
by parv (Parson) on Apr 12, 2008 at 09:31 UTC
    ... warning comes up only when using, well, warnings pragma (otherwise string is used as a zero).
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[d/l]

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