insert blank line between lines

Shell Programming and Scripting
1

Hello,

I am trying to write a script that will count the number of characters for each line in a file and all the lines that have less than 80 characters and that are ending with a period, I want it to insert a blank line after them immediately. But, for whatever reason the condition if [[ "$len" -lt "$MINLEN" && "$line" =~ \[*\.\] ]] is not evaluated. So, nothing happens to the file. It just prints the line as is . It does not add the blank space after a line that has less than 80 characters and that end with a period. Can you please help me?

 
 
#!/bin/bash
MINLEN=80
# Assume lines shorter than $MINLEN characters ending in a period
#+ terminate a paragraph. 
while read line 
do
echo "$line" 
len=${#line}
if [[ "$len" -lt "$MINLEN" && "$line" =~ \[*\.\] ]]
then echo    
fi           
done
exit
2 
awk 'length($0)<80 && substr($0,length($0),1)=="." { print ; print "\n" ;next } 1' input_file
3 
sed '/.\{80\}/!{/\.$/G;}' file

awk '{print $0 (length<80 && /\.$/ ? "\n" : "")}' file

while IFS= read -r line; do
    printf '%s\n' "$line"
    [ ${#line} -lt 80 ] && expr "$line" : '.*\.$' >/dev/null && printf '\n'
done < file

Regards,
Alister

4 
$ ruby -ne ' print ( $_.size<80 && /\.$/ )? $_+"\n": $_' file