It doesn't account for anywhere near the whole difference, but in a tight loop like that Python's going to be spending a good chunk of its time re-compiling the regex from the raw string literal every iteration. Hoist the regex definition out of the loop like so and it'll probably run about 30% faster:

  #!/usr/bin/env python3

  import re

  with open('logs1.txt', 'r') as fh:
      regex = re.compile(r'\b\w{15}\b')
      for line in fh:
          if regex.search(line): print(line, end='')

Perl almost certainly does this by default for regex literals, and that's a fair advantage for the "kitchen sink" style of language design versus orthogonal features (regex library, raw strings) that Python uses.

Running a different test the slowest part of the python script is the startup time, otherwise they're identical:

    [admin@localhost ~]$ time ./test.py
    real 0m0.295s
    user 0m0.158s
    sys 0m0.138s

    [admin@localhost ~]$ time ./test.pl
    real 0m0.164s
    user 0m0.158s
    sys 0m0.006s

    #!/usr/bin/env perl
    use 5.16.3;

    open my $fh, '<', 'logs1.txt';
    while (<$fh>) {
    chomp;
    if (/\b\w{15}\b/) {}
    }
    close $fh;

    #!/usr/bin/env python

    import re
    regex = re.compile(r'\b\w{15}\b')

    with open('logs1.txt', 'r') as fh:
     for line in fh:
      if regex.search(line):
       continue

The python code should run much faster if you don't print..

Edit: perl is still faster, to be clear