OS X (Apple)

DP=3
MOD=1000

function readnum {
        OLDIFS="$IFS"
        IFS="."
                set -- $1 # Set $1, $2, etc, splitting on "."
        IFS="$OLDIFS"

        N=$1
        FRAC=$2

        [ "$N" = "0" ] && N=""

        for((X=0; X<DP; X++))
        do
                D="${FRAC:$X:1}"
                [ -z "$D" ] && D="0"
                N="$N$D" # Prepend digits to N
        done
}

readnum "0.5"

echo "Integer $N is fixed point $((N/MOD)).$((N%MOD))"

#!/usr/local/bin/dash
# heredoc.sh
IFS="$IFS"'.'

read -r INT FLOAT <<EOF
$1
EOF
echo "$INT $FLOAT"

Last login: Wed Nov  7 19:10:03 on console
AMIGA:amiga~> cd Desktop/Code/Shell
AMIGA:amiga~/Desktop/Code/Shell> chmod 755 heredoc.sh
AMIGA:amiga~/Desktop/Code/Shell> ./heredoc.sh 123.456
123 456
AMIGA:amiga~/Desktop/Code/Shell> _

	        .--.
	        \   \
	         .   .
	         |   |
	         |   |
	         |   |
	    ____/     `-----------.
	   /                       )
	  |           +----------.'
	  |                       )
	  |           +---------.'
	  |                      )
	  |           +--------.'
	   \                    )
	    '------------------'

IFS="$IFS"'.'

oldIFS=$IFS
IFS="$IFS"'.'
# shell code that needs the modified IFS
# restore the old IFS
IFS=$oldIFS
# normal shell code

(
# this is a sub shell
IFS="$IFS"'.'
# shell code that needs the modified IFS
)
# in the main shell there is the old IFS

IFS="$IFS"'.' read ...
# after the command there is the old IFS

(
# this is a sub shell
IFS="$IFS"'.'
# shell code that needs the modified IFS
)
# in the main shell there is the old IFS

	        .--.
	        \   \
	         .   .
	         |   |
	         |   |
	         |   |
	    ____/     `-----------.
	   /                       )
	  |           +----------.'
	  |                       )
	  |           +---------.'
	  |                      )
	  |           +--------.'
	   \                    )
	    '------------------'