If the ip address at the end is separated by a known character from the rest of the line, say a space, then:

use feature ":5.14";
use warnings FATAL => qw(all);
use strict;
use Data::Dump qw(dump pp);

my $s = ' '; # Separator
say s/\A(.*)$s(.+)\Z/$2$s$1/r for 

split /\n/, <<'END';
djshajfh kjwhjhfh aks81368`17`tr `" " \ 12.123.12.001
fueiwqgfh 9ur`023456789-ds 10.1.999.002
fdfhfsdh she  eq3435235b ^&*(O&*()^&*( 10.20.30.40
fdfhfsd1111.11.11.11hheq3435235b ^&*(O&*()^&*( 1.2.3.4
fdfhfsdhheq341111.3333.4444.11.2235235b ^&*(O&*()^&*( 111.222.333.444
END
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Produces

12.123.12.001 djshajfh kjwhjhfh aks81368`17`tr `" " \
10.1.999.002 fueiwqgfh 9ur`023456789-ds
10.20.30.40 fdfhfsdh she  eq3435235b ^&*(O&*()^&*(
1.2.3.4 fdfhfsd1111.11.11.11hheq3435235b ^&*(O&*()^&*(
111.222.333.444 fdfhfsdhheq341111.3333.4444.11.2235235b ^&*(O&*()^&*(