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Editorial Team
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Asked: 2026-05-26T08:23:59+00:00

I’ve inherited the following Perl code, and I’m having difficulty understanding what exactly the

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I’ve inherited the following Perl code, and I’m having difficulty understanding what exactly the index and match functions are doing here:

my $url = $ENV{'REQUEST_URI'};
my $loc = $url;
$loc =~ s/\/parks\///i;
my $page = substr($loc, 0, index $loc, "_");

I know that index(str, char) returns the index of a particular character, so what function does index $loc serve? Is it simply returning the length?

I’m also confused by the line $loc =~ s/\/parks\///i; which matches the phrase “/parks/” in the url. I don’t see the purpose of it, because whether it returns true or false, isn’t $loc still a string containing the url? What should I expect to be contained in $page?

I am very new to Perl so I appreciate that there will be some nuances that I haven’t yet grasped.

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1 Answer

  1. Editorial Team

    Perl’s slightly cavalier approach to parenthesis might be confusing you a little here. The calls to substr and index might be more clearly written as:

    my $page = substr($loc, 0, index($loc, "_"));

    It’s looking for the first occurrence of ‘_’ in $loc and truncating the variable at that point.

    Also, the substitution operator would be easier to understand if you used alternative delimiters.

    $loc =~ s|/parks/||i;

    It means “look for the first occurrence of “/parks/” in $loc and replace it with an empty string (i.e. remove it).

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