Your regular expression does match because it is really present inside the string:
"[someRandomName]." (The text in bracket is the matched text)
"[someRandomName]-"

What you want is anchoring the regular expression. Try adding a '^' at the beginning and a '$' at the end of the regular expression. The Regex will then try to match against the whole string, and not only on a part of it:

/^[A-Z0-9]+[A-Z0-9-]+[A-Z0-9]{1}$/i

Hope this helps. See perlre for more infos about this

#!/usr/bin/perl -w
use strict;
my $domain = $ARGV[0];
print "Got $domain\n";
if ($domain =~ /^[A-Z0-9]+[A-Z0-9-]+[A-Z0-9]$/i)
{
        print "$domain matched\n\n";
}
else
{
        print "$domain did not match\n\n";
}
__END__
Got someRandomName.
someRandomName. did not match

Got someRandomName-
someRandomName- did not match

Got someRandomName
someRandomName matched

Got someRandomName-X
someRandomName-X matched

Got someRandomName-Foo
someRandomName-Foo matched
[download]

<kbd>--
my $OeufMayo = new PerlMonger::Paris({http => 'paris.mongueurs.net'});</kbd>