I keep getting error "Directory stack not that deep" I have adjusted the <= sign but to no avail

Question

My code below wont run due to " Directory stack not deep error...Pls tell me what's wrong. I suspect the error is in the while loop. I have made several adjustments but nothing works

#!/bin/csh -f
#set verbose
#Lab 4 Preprocessing

setenv DATA /gaia/home/copara/Documents/eseis/su
echo $ DATA

setenv PROCDATA /gaia/home/copara/Documents/eseis/processed
echo $ PROCDATA

set ifldr=1001
echo $ifldr

while ($ifldr <=1162)

    setenv shot shotgather.su
    setenv shotfile $PROCDATA/$ifldr$shot

    setenv chan channel.su
    setenv chanfile $PROCDATA/$ifldr$chan

    setenv vibe vibro.su
    setenv vibefile $PROCDATA/$ifldr$vibe

    setenv corr corr.su
    setenv corrfile $PROCDATA/$ifldr$corr

    suwind key=fldr min=$ifldr max=$ifldr <$DATA/data.su>$shotfile
    suwind key=tracf min=1 max=144 <$shotfile>$chanfile
    suwind key=tracf min=145 max=145 <$shotfile>$vibefile
    suxcor <$chanfile sufile=$vibefile vibroseis=7000 >$corrfile

    @ifldr=$ifldr+1
end

Answer 1

Add a space between <= and 1162 and after @. csh is space-sensitive. Here is an example:

% @a=1
@a=1: Command not found.
% @ a=1
% echo $a
1
% @ a=$a+1
@: Badly formed number.
% @ a=$a + 1
% echo $a
2
% @ a++
% echo $a
3