Prepending lines with file name

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# 1  
Old 08-07-2011
Prepending lines with file name

I have a number of dat-files, such as abc.dat, def.dat etc, as follows:
2011-07-01  100.0
2011-07-02  101.0
2011-07-03  101.7

I want to prepend the file with the base file name; so for abc.dat it would result in the following:
abc  2011-07-01  100.0
abc  2011-07-02  101.0
abc  2011-07-03  101.7

How do I achieve that? The closest I currently have is the following:
for file in *.dat; do
  $prepend=`echo $file | cut -d "." -f 1`
  sed -i '' -e 's/^/$prepend /' $file

Also, how can the same command be used to delimit by tab (\t) instead of space?
# 2  
Old 08-07-2011
It can be done in single line by Perl:
perl -i -pe '$ARGV=~s/\..*//;$_="$ARGV\t$_"' *.dat

# 3  
Old 08-07-2011
Thank you for your response. And you may already have seen that the title of the post should read: "Prepending lines with file name"
Code works nicely by the way. Nonetheless, can you also achieve the same in the shell script?
# 4  
Old 08-07-2011
It will work all the same if you put it into shell script like this:
perl -i -pe '$ARGV=~s/\..*//;$_="$ARGV\t$_"' *.dat

# 5  
Old 08-07-2011
Ok, thanks again.
# 6  
Old 08-07-2011
bash only
for file in *.dat;do while read line;do echo -e "${file/.dat/}"\\t"$line";done < "$file";done

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