while (<>) {
    # do something with $_ here
}

##</code><code>##

unshift(@ARGV, '-') unless @ARGV;
while ($ARGV = shift) {
    open(ARGV, $ARGV);
    while ($_ = readline(<ARGV>)) {
        # do something with $_
    }
}

##</code><code>##

%hash = ();
{
    my @keys   = qw ( a, b, c);
    my @values = 1..3;
    for ( my $c = 0; $c <= $#keys; $c++ ) {
        $hash { $keys [$c] } = $values [ $c ];
    }
}

##</code><code>##

@hash { qw (a, b, c) } = 1..3;

##</code><code>##

{ # block for local
    local $/ = ''; # paragraph mode
    path( $dhcpcdfile )->edit_lines(
        sub {
            if( m/                       # match this:
                  ^\s*                   # zero or more whitespace chars at line begin
                  profile                # followed by the word "profile"
                  \s+                    # one or more whitespace
                  static_                # then "static_"
                  $ip_params{interface}  # the value for key "interface" in %ip_params
                 \b                      # a word boundary
                  .*                     # zero or more following chars
                  \n                     # and a newline
                  /mx                    # in a multiline block
            ) {
                # alter this section
                s/                       # match and substitute
                  ^\s*                   # zero or more whitespace chars at line begin
                  static                 # word "static"
                  \s+                    # one or more whitespace chars
                  (\w+)                  # a word (see perlre) captured in $1
                  =                      # equal sign
                  \K                     # but keep what was matched so far
                  .*                     # any following chars
                /                        # against
                  $ip_params{$1}         # the value of key $1 (see above) in hash %ip_params
                /gmx;                    # globally in a multiline block (for "x" see perlre)
            } # endif
        } # end of sub
    );
} # end of "local $/" block