#! perl
use strict;
use warnings;

my $re1 = qr{ ^ [\w-]+ $ }x;
my $re2 = qr{ ^  \d+   $ }x;

while (<DATA>)
{
    chomp;
    printf "%s : %s\n", $_, /$re1/ && !/$re2/ ? 'yes' : 'no';
}

__DATA__
foo
1foo
foo2
3foo4
foo5bar
87
foo-bar
foo42-baz
foo17@12