I've noticed a huge (10x) performance difference between two algorithims. It's not obvious (to me) why the difference is so great. I'm trying to parse each line of a file that's already been read into an array. There are three different lines that are interesting. They are in the @patterns array. I have an outer loop to iterate over the source lines and an inner loop to iterate over the patterns. I store the interesting lines in another array. With a particular data set this code takes around 30 seconds to execute. 
    my @patterns = ("SDC: HUT time changed: 0",
                    "BATT: Cap=0\\(watt-min\\) HUT=0\\(min\\) 0\\(hrs\
+\) state=GOOD->BAD",
                    "BATT: Log battery system condition GOOD->BAD");

    my @events;
    
    foreach my $line (@$srcRef)
    {
        foreach my $pattern (@patterns)
        {
            if ($line =~ /$pattern/)
            {
                push(@events, $line);
                last;
            }
        }
    }

[download]
Unrolling the inner loop like so, results in 3 second execution and appears to produce the same results. Why the 10x hit with the nested loops? What am I missing? Thanks. 
    foreach my $line (@$srcRef)
    {
        if ($line =~ /SDC: HUT time changed: 0/)
        {
            push(@events, $line);
        }
        elsif ($line =~ /BATT: Cap=0\(watt-min\) HUT=0\(min\) 0\(hrs\)
+ state=GOOD->BAD/)
        {
            push(@events, $line);
        }
        elsif ($line =~ /BATT: Log battery system condition GOOD->BAD/
+)
        {
            push(@events, $line);
        }
    }

[download]

In reply to performance explanation needed by yoganaut

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