You need "=" in substitution field. Replace "\1" with "$1" per warnings. 
use strict;
use warnings;
use Test::Simple tests=>1;

my $input_string = qq(parameter=TO_DATE('1900-01-01','YYYY-MM-DD')\n);
my $desired_output = qq(parameter="TO_DATE('1900-01-01','YYYY-MM-DD')"
+\n);

my $output = $input_string =~ s/=(.*)/="$1"/r;

ok( $output eq $desired_output, $output );

[download]

OUTPUT:

1..1
ok 1 - parameter="TO_DATE('1900-01-01','YYYY-MM-DD')"
#

[download]
Bill

In reply to Re^2: replacing equal to operator by BillKSmith
in thread replacing equal to operator by ty_sopw

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