#! perl
use Modern::Perl;

while (<DATA>)
{
    chomp;

    if (/ ^ (?: (?: -? \d+) | (?: -? \d+ \. \d+)) $ /x)
    {
        say 'Yes, ', $_, ' is a number';
    }
    else
    {
        say 'No, ',  $_, ' is not a number';
    }
}

__DATA__
4
-7
0.656
-67.35555
5.
56F
.32 
-.04
[download]

Output:

 2:17 >perl 417_SoPW.pl
Yes, 4 is a number
Yes, -7 is a number
Yes, 0.656 is a number
Yes, -67.35555 is a number
No, 5. is not a number
No, 56F is not a number
No, .32  is not a number
No, -.04 is not a number

 2:17 >
[download]

Some notes:

• | is bitwise-OR outside a regex, and alternation in a regex. For logical OR, use || (or or).

• Within a regex, a dot matches any character. To match the decimal point, you need to escape it: “\.”.

• Prefer chomp to chop — the former removes a line-termination if present, the latter removes the last character regardless.

Hope that helps,

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