It looks like a flip-flop ... (update: in Perl you can also use a variable as it's own flag provided there are no empty or zero values for it permitted in the actual data)

# ...

$sth->bind_columns( undef,\$alias);
my $key = 0;
while($sth->fetchrow_array()) {

    if ( $key  ) {
        print "$key, $alias\n";
        $key = 0;
    }
    else{
        $key = $alias;
    }
}
[download]

or if you later realise you need to store the pairs anyway... ;)

$sth->bind_columns( undef,\$alias);
my %hash;
my $key = 0;
while($sth->fetchrow_array()) {

    if ( $key  ) {
        $hash{ $key } = $alias;
        # print "$key, $alias\n";
        $key = 0;
    }
    else{
        $key = $alias;
    }
}
[download]

(updated to get rid of an unnecessary step)

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.