open (NETSTATS,"$input_file");
$/ = "\nnet '";

my @field_names = ( 'wire capacitance', 'wire resistance',
           'number of loads', 'number of pins', 'total wire length' );

while (<NETSTATS>) {
    chomp;  # removes $/ from end of string;
    warn "got record # $.\n" if ( $. % 50000 == 0 );  # this belongs on STDERR, IMO
    next unless (/^([^']+)'/);
    $NetName = $1;

    my %field_val = ();
    for my $field ( @field_names ) {
        if ( /$field:\s+([\d.]+)/ ) {
            $field_val{$field} = $1;
        }
    }
    # ....
}