I have a loop here, that is requiring a lot of time to run. (I believe) The purpose is to read an edge list and convert it into a hash, there's about 30,000 nodes in this graph, but 90,000 lines. So there are loops which need to be eliminated. (Graph is undirected.) The data is such that:
0 1
1 2
1 3
1 4
2 4
4 5

With my code looking like: 
my %edgeHash;
my %countHash;
while(<stdin>){

    # Reading an edge list
    if(/^\s*([0-9]+)\s+([0-9]+)\S*$/){
        my $a = "$1";
        my $b = "$2";
        my $good = "1";

        # Eliminate loops
        foreach my $item (keys %edgeHash){
            foreach my $item2(@{$edgeHash{$item}}){
                if($item2 eq $b){
                    $good = "0";
                }
            }
        }

        # Add items to the edge hash
        if($good eq "1"){
            if(exists($edgeHash{$a})){
                push @{$edgeHash{$a}}, $b;
            }else{
                push @{$edgeHash{$a}}, $b;
            }
        }
    }
}

[download]

In reply to H of A optimization by abitkin

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • 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! —
  • 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:
    & &amp;
    < &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.