I apologize, my while loop exit code was wrong. No wonder the regex beat getpwnam. Here is the correct code and results. Stick wirh getpwnam().

#!/usr/bin/perl -w

use Benchmark;

for $x (1, 50, 1000, 3000, 6000){

timethese (1000,{ 
        "getpwnam${x}" => q {
        $there=getpwnam("x${x}")
        },
        "regex${x}" => q {open(PASSWD,"/etc/passwd"); 
        while(<PASSWD>)
        { if (/^x${x}:/){$alsothere=1; last};
        }
        close PASSWD;},
});
}


Benchmark: timing 1000 iterations of getpwnam1, regex1...
 getpwnam1:  0 wallclock secs ( 0.12 usr +  0.06 sys =  0.18 CPU) @ 55
+55.56/s (n
=1000)
            (warning: too few iterations for a reliable count)
    regex1:  0 wallclock secs ( 0.41 usr +  0.02 sys =  0.43 CPU) @ 23
+25.58/s (n
=1000)
Benchmark: timing 1000 iterations of getpwnam50, regex50...
getpwnam50:  1 wallclock secs ( 0.28 usr +  0.02 sys =  0.30 CPU) @ 33
+33.33/s (n
=1000)
            (warning: too few iterations for a reliable count)
   regex50:  1 wallclock secs ( 0.80 usr +  0.04 sys =  0.84 CPU) @ 11
+90.48/s (n
=1000)
Benchmark: timing 1000 iterations of getpwnam1000, regex1000...
getpwnam1000:  2 wallclock secs ( 2.41 usr +  0.20 sys =  2.61 CPU) @ 
+383.14/s (
n=1000)
 regex1000:  9 wallclock secs ( 8.52 usr +  0.13 sys =  8.65 CPU) @ 11
+5.61/s (n=
1000)
Benchmark: timing 1000 iterations of getpwnam3000, regex3000...
getpwnam3000:  9 wallclock secs ( 7.36 usr +  0.38 sys =  7.74 CPU) @ 
+129.20/s (
n=1000)
 regex3000: 28 wallclock secs (24.94 usr +  0.54 sys = 25.48 CPU) @ 39
+.25/s (n=1
000)
Benchmark: timing 1000 iterations of getpwnam6000, regex6000...
getpwnam6000: 16 wallclock secs (14.44 usr +  0.77 sys = 15.21 CPU) @ 
+65.75/s (n
=1000)
 regex6000: 50 wallclock secs (49.24 usr +  1.17 sys = 50.41 CPU) @ 19
+.84/s (n=1
000)
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Forgiveness Please.

Beating myself with a bamboo cane as I speak.