Parameter problem with plink and PowerShell

$plink='C:\Program Files (x86)\PuTTY\plink.exe'$switch="172.20.19.50"$commands="c:\scripts\cmd.txt"$username=Read-Host"User name"$pw=Read-Host-Prompt"Enter password"-AsSecureString$plink-l$username-pw$pw-m$commands-ssh$switch

Youmustprovideavalueexpressionontheright-handsideofthe'-'operator.Atline:7char:8Unexpectedtoken'l'inexpressionorstatement.Atline:7char:9Unexpectedtoken'username'inexpressionorstatement.Atline:7char:11Unexpectedtoken'-pw'inexpressionorstatement.Atline:7char:21Unexpectedtoken'pw'inexpressionorstatement.Atline:7char:25Unexpectedtoken'-m'inexpressionorstatement.Atline:7char:29Unexpectedtoken...