my $content = '<entry key="maxcompdatastripe" value="41943040" />';
my $maxreplacement_value = ' "20917520" merge="keep" ';
$content =~ s/(<entry key="maxcompdatastripe" value=")[^"]*("\s*\/>)/$1$maxreplacement_value$2/g;
print "Content: $content\n";

Expected results: 
<entry key="maxcompdatastripe" value="20917520" merge="keep" />

Actual Results:
Content: <entry key="maxcompdatastripe" value=" "20917520" merge="keep" " />