The problem is fixed by specifying your regex using m{} instead of ??.

#!/usr/bin/perl
use strict ;
########################################################
######## START MAIN ####################
my @STAGE=(
    '/stage/core/HPUX/PA-RISC-64/64bit/rdbms/10.2.0.1.0/dvd2/clusterwa
+re',
    '/stage/core/HPUX/PA-RISC-64/64bit/rdbms/patches/10.2.0.4.0/Disk1'
);

for my $i (0..5){
   my $o_vers ;
   my $j = $i & 1;
   $o_vers = $1 if $STAGE[$j] =~ m{/rdbms/([\d.]+)/};
   $o_vers = $1 if $STAGE[$j] =~ m{/rdbms/patches/([\d.]+)/};
   print "Iteration# $i: Version is: $o_vers\n" ;
}
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Also note, you could combine your two regex's like so:

for my $i (0..5){
   my $j = $i & 1;
   my $o_vers = $STAGE[$j] =~ m{/rdbms/(?:patches/)?([\d.]+)/} ? $1 : 
+'';
   print "Iteration# $i: Version is: $o_vers\n" ;
}
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- Miller