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#!/usr/bin/env perl

use warnings;
use strict;

my $today = get_cur_time();

while (<DATA>) {
    if (/API call error/) {
        my ($date, $time, $suffix) = split;
        $date   =~ s/\[//;
        $suffix =~ s/]//;
        if ($date eq $today) {
            print "Error occurred: date=$date, time=$time $suffix\n";
        }
    }
}
exit;

sub get_cur_time  {
    my ($Day, $Month, $Year) = (localtime(time))[3..6];
    $Year   += 1900;
    $Month  = sprintf '%02d', $Month + 1;
    $Day    = sprintf '%02d', $Day;
    return "$Month/$Day/$Year";
}

# Example: Log File Line Containing Date
__DATA__
[01/25/2008 4:33 AM] foo
[01/25/2008 5:33 AM] bar
[01/25/2008 10:01 AM] API call error
[01/25/2008 11:55 PM] baz
[01/26/2008 10:01 AM] API call error
[download]

This prints out:

Error occurred: date=01/25/2008, time=10:01 AM
[download]