use warnings ;
use strict ;

my %h = ( 'a' => 1, 'b' => 1, 'c' => 1 ) ;
my $str ;                                
foreach ( keys %h ) {  
  $str .= "$_ "  
}
xyz( $str ) ;

sub xyz {
  print shift ;
}

##</code><code>##

use warnings ;
use strict ;

my %h = ( 'a' => 1, 'b' => 1, 'c' => 1 ) ;
xyz( "keys(%h)" ) ;

sub xyz {
  print shift ;
}