Processing multi-line input - Loop vs Regex - regex

Question

I am trying to look for a specific keyword in multi-line input string like this,
this is input line 1
this is the keyword line
this is another input line
this is the last input line
The multi-line input is stored in a variable called "$inputData". Now, I have 2 ways in mind to look for the word "keyword",
Method 1:
Using split to put the lines into an array using "\n" separator and iterate and process each line using foreach loop, like this,
my #opLines = split("\n", $inputData);
# process each line individually
foreach my $opLine ( #opLines )
{
# look for presence of "keyword" in the line
if(index($opLine, "keyword") > -1)
{
# further processing
}
}
Method 2:
Using regex, as below,
if($inputData =~ /keyword/m)
{
# further processing
}
I would like to know how these 2 methods compare with each other and What would be the better method with regards to actual code performance and execution time. Also, is there a better and more efficient way to go about this task?

Answer 1

my #opLines = split("\n", $inputData);
Will create variable #opLines, allocate memory, and search "\n" trough whole $inputData and write found lines into it.
# process each line individually
foreach my $opLine ( #opLines )
{
Will process the whole bunch of code for each value in array #opLines
# look for presence of "keyword" in the line
if(index($opLine, "keyword") > -1)
Will search for the "keyword" in each line.
{
# further processing
}
}
And comapare
if($inputData =~ /keyword/m)
Will search for the "keyword" and stops when find first occurrence.
{
# further processing
}
And now guess, what will be faster and consume less memory (which affects speed as well). If you are bad in guessing use Benchmark module.
According documentation m regular expression modifier: Treat string as multiple lines. That is, change "^" and "$" from matching the start or end of line only at the left and right ends of the string to matching them anywhere within the string. I don't see neither ^ nor $ in your regexp so it is useless there.