$query =~ s/$value/$replace/i;

The problem is that $value contains something like $Id, and the $ when interpreted as a regex means "match the end of the string", not "match a dollar sign". You can fix that by writing 

s/\Q$value\E/$replace/i;

[download]

instead.

Fwiw this is how I'd solve the same task: 

my @array_1 = ("\$Id_run_query=1", "\$name_run_query=xyz", "db_query_r
+un_query=select * from meter where metetid=\$Id and metername=\$name"
+);
my $query;
my %replace;

foreach(@array_1){
    if (m/^db_query_run_query=(.*)/i){
        $query = $1
    }
    elsif (/(\$\S+)_run_query=(.*)/) {
        $replace{$1} = $2;
    }
}
my $replace_re = join '|', map quotemeta, keys %replace;
$query =~ s/($replace_re)/$replace{$1}/ig;

print "===>$query\n";

[download]

The call to quotemeta does the same as \Q...\E in the regex.

Perl 6 - the future is here, just unevenly distributed

In reply to Re: Regex is not working by moritz
in thread Regex is not working by Rahul Gupta

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.