Hi Mjpaddy,
..which can make a sentence into two equal part or half or partially half

Others have answered you well, but what got my attention was the two equal part or half "wordings", in your question. Though I might be wrong, in the sense that the OP's example might have shown what s/he might want.

But that being said, IMHO, one can get the sentence into two equals, considering all the character in the sentence space in inclusive, like so:

use warnings;
use strict;

my $wd =
'Perl 5 is a highly capable, feature-rich programming language with ov
+er 27 years of development.';
my $midpt = ( split //, $wd ) / 2 ;
print join(
    $/ => (
        "First-Half:",  substr( $wd, 0, $midpt ),
        "Second-Half:", substr( $wd, $midpt )
    )
), $/;
[download]

First-Half:
Perl 5 is a highly capable, feature-rich program
Second-Half:
ming language with over 27 years of development.
[download]