#!/bin/perl -w
use strict;
my $numbers="1 1.0 3.547 92.34 12 .25 23.00 23.01 343.2234";

# I guess that's what you were looking for
while($numbers=~/(?<![\.\d]) # first no digits or .
                 (\d+)       # digits
                 (?!\d*\.\d) # then no digits, . and digits
                /gx)
  { print "$1 is an integer\n"; }

print '-' x 20, "\n";

# the same thing slightly simpler
while($numbers=~/(?:\A|[^\d\.])  # catches the character before a number or the start of the string
                 (\d+)           # digits
                 (?!\d*\.\d)     # then no digits, . and digits
                /gx)
  { print "$1 is an integer\n"; }
  
# much simpler I think
while($numbers=~/([\d\.]+)/g)         # catch all numbers   
  { if( $1=~ /^(\d+)$/)               # keep only integer ones
      { print "$1 is an integer\n"; } # this $1 from the if regexp
  }
  print '-' x 20, "\n";

# now maybe 1.0 is considered an integer
while($numbers=~/(\d+(?:\.(\d+))?)/g)
  { my $nb= $1;                                              # get all numbers
    print "$nb is an integer\n" if( !$2 || ($2=~ /^0+$/) );  # keep those with no decimal parts 
                                                             # or with a deciaml part only made of 0's
   }